#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL a[maxn];
map<LL,LL>map1;
int main(void){
   	cin.tie(0);std::ios::sync_with_stdio(false);
    LL t;cin>>t;
    while(t--){
        LL n,k;cin>>n>>k;
        map1.clear();
        for(LL i=1;i<=n;i++) cin>>a[i];
        LL ans=-1e18;
        for(LL i=n;i>=max((LL)1,n-1000);i--){
            for(LL j=i-1;j>=max((LL)1,i-10000);j--){
                ans=max(ans,i*j-k*(a[i]|a[j]));
            }
        }
        cout<<ans<<"\n";
    }
   	return 0;
}
